package ca.scotthyndman.as2haxe.dom;

/**
 * Descriptor for a child property of an AST node. A child property is one whose
 * value is an {@link ASTNode}.
 */
public class ASChildPropertyDescriptor extends ASPropertyDescriptor {

	/**
	 * Child type. For example, for a node type like CompilationUnit, the
	 * "package" property is PackageDeclaration.class
	 */
	private final Class childClass;

	/**
	 * Indicates whether the child is mandatory. A child property is allowed to
	 * be <code>null</code> only if it is not mandatory.
	 */
	private final boolean mandatory;

	/**
	 * Creates a new child property descriptor with the given property id. Note
	 * that this constructor is declared package-private so that property
	 * descriptors can only be created by the AST implementation.
	 * 
	 * @param nodeClass
	 *            concrete AST node type that owns this property
	 * @param propertyId
	 *            the property id
	 * @param childType
	 *            the child type of this property
	 */
	ASChildPropertyDescriptor(Class nodeClass, String propertyId,
			Class childType, boolean mandatory) {
		super(nodeClass, propertyId);
		if (childType == null || !ASTNode.class.isAssignableFrom(childType)) {
			throw new IllegalArgumentException();
		}
		this.childClass = childType;
		this.mandatory = mandatory;
	}

	/**
	 * Returns the child type of this property.
	 * <p>
	 * For example, for a node type like CompilationUnit, the "package" property
	 * returns <code>PackageDeclaration.class</code>.
	 * </p>
	 * 
	 * @return the child type of the property
	 */
	public final Class getChildType() {
		return this.childClass;
	}

	/**
	 * Returns whether this property is mandatory. A property value is not
	 * allowed to be <code>null</code> if it is mandatory.
	 * 
	 * @return <code>true</code> if the property is mandatory, and
	 *         <code>false</code> if it is may be <code>null</code>
	 */
	public final boolean isMandatory() {
		return this.mandatory;
	}
}
